FIG. 1 depicts a diagram of the salient components of wireless telecommunications system 100 in accordance with the prior art. Wireless telecommunications system 100 comprises: wireless terminals 101-1, 101-2, 101-3, and 101-4, cellular base stations 102-1, 102-2, and 102-3, Wi-Fi base stations 103-1 and 103-2, and wireless infrastructure 111, interconnected as shown. Wireless telecommunications system 100 provides wireless telecommunications service to all of geographic region 120.
The salient advantage of wireless telecommunications over wireline telecommunications is the mobility that is afforded to wireless service subscribers, who are the users of the wireless telecommunications system. On the other hand, the salient disadvantage of wireless telecommunications lies in that fact that because the wireless terminals are mobile, an interested party might not be able to readily ascertain the location of a terminal.
Such interested parties might include both i) the wireless service subscriber using the wireless terminal and ii) remote parties. There are a variety of reasons why the subscriber might be interested in knowing his or her own location. For example, the subscriber might be interested in telling a remote party where he or she is. Or the subscriber might be interested in knowing how to navigate from where he or she is to another location.
There are a variety of reasons why a remote party might be interested in knowing the location of the subscriber. For example, the recipient of a 911 emergency call from a wireless terminal might be interested in knowing the location of the terminal so that emergency services vehicles can be dispatched to that location.
A variety of techniques are known in the prior art for locating a wireless terminal. The wireless terminal can be tracked by using any of these techniques repetitively. In general, the confidence with which a tracking system can estimate the location of a wireless terminal at any instant is a function of the frequency at which the location is determined and the mobility of the terminal. This is because the tracking system must estimate the location of the terminal for those instants between when the terminal is actually located. The longer the interval between when the terminal is located, the less confidence the tracking system can have in estimating the location at each instant during the interval. Therefore, the confidence with which a tracking system can estimate the location of a wireless terminal at any instant is a function of the frequency at which the terminal is actually located.
Although repeating a prior-art location technique over and over frequently might be practical for tracking one wireless terminal, it is not practical for tracking a large number of terminals. The reason is that the process of locating a wireless terminal consumes limited resources—such as wireline and wireless bandwidth—and those resources are quickly exhausted when the location is re-determined frequently for a large number of terminals.
The location of large numbers of wireless terminals at each instant does not necessarily require that the location of each terminal be re-determined frequently. This is because there are situations in which the location of a wireless terminal can be stated, with an acceptable degree of confidence, even though the location of the terminal is re-determined less frequently. For example, when the empirical evidence suggests that the wireless terminal is stationary or moving slowly, then the frequency with which the terminal is located can be reduced. As another example, when a tracking system in the prior art observes that a wireless terminal is “home” 99% of the time from Midnight to 6:00 AM, it is reasonable—absent other factors—to locate that wireless terminal infrequently from Midnight to 6:00 AM and yet estimate, with an acceptable degree of confidence, that the terminal is home at each instant between Midnight and 6:00 AM. In contrast, when a tracking system observes that a wireless terminal is “home” 11% of the time from Midnight to 6:00 AM, it is not reasonable to locate that wireless terminal infrequently from Midnight to 6:00 AM and yet to estimate that the terminal is at home at each instant between Midnight and 6:00 AM.
Although various techniques in the prior art attempt to reduce the rate at which the locations of large numbers of terminals are re-determined, the overall tracking process can still exhaust the limited resources that are utilized.